Samsung SSD 840 EVO mSATA 1TB Review

It's fair to say the original SSD 840 EVO launch was very successful. Thanks to its competitive performance, good value and tasty feature set, we awarded the entire range our Premium Grade award. Now Samsung is back with another set of SSD 840 EVO drives, having shrunk the entire range into the tiny mSATA form factor. And yes, this includes the 1TB model, and it's this one we're looking at today - a world's first for drives this size.

Designed as an upgrade for ultra-thin laptops as well as desktops with mSATA capabilities, the fact that something so small can store up to 1TB of data is amazing in and of itself. For anyone unfamiliar with mSATA, the comparison shot below shows its size relative to the 2.5-inch version of the SSD 840 EVO.

Click to enlarge - Behold, the world's first 1TB mSATA SSD

The better news is that the mSATA version of the EVO has the same recommended price as the regular one, so there's no premium for the smaller size. We've listed £509.99 as the MSRP, since this is in line with that of the original drive, but with 1TB SSD 840 EVO models selling for around £460 it could well be less by the time it hits retailers' shelves. Of course, mechanical drives are still far cheaper, but equally they're much larger and slower. As well as the 1TB model, the 120GB, 250GB and 500GB ones will also have mSATA equivalents, but not the 750GB one. Also, unlike the 2.5-inch drives, there will be no upgrade bundles with mSATA to USB or mSATA to SATA adaptors supplied - a somewhat surprising choice, particularly for laptop upgrades.

The 1TB drive features four separate NAND packages (2 on each side of the PCB), each with a whopping 256GB crammed inside. Samsung is sticking with 3-bit MLC (TLC) NAND for the EVO mSATA range, produced on a 19nm process. Though many have previously raised concerns about the endurance and performance of such NAND, the latter appears to be mostly unfounded. Torture tests elsewhere also reveal such NAND to be easily capable of surviving huge workloads, while the latest figures from Samsung suggest the original 840 EVO drives can survive at least 2,500 program/erase cycles. The company also offers a fairly standard three year warranty, and has a couple of tricks to address the performance side of things.

Click to enlarge - A size comparison of the mSATA and 2.5-inch models of the SSD 840 EVO

The first such trick is TurboWrite, whereby a fixed portion of the TLC NAND (with fixed address space) is treated by the drive as SLC NAND when writing. As such, it stores data in one of two states rather than one of eight, leading to easier and faster writes. All writes regardless of size are processed in this way, then when the drive is idle, they're flushed to the regular NAND. If you filled the TurboWrite buffer with a single write task with no idle time, the drive will drop to lower write speeds (from 520MB/sec to 380MB/sec for the 1TB model) as it's forced to write to the slower NAND areas. The size of the buffer varies by drive capacity, but for the 1TB drive it's a healthy 12GB.

Another trick is the software based RAPID Mode, essentially a one click RAM-caching mode available through Samsung's Magician software, with the pending 4.3 version set to add support to the SSD 840 PRO as well as the EVO mSATA models. It's limited to one drive in Windows 7 or 8, and won't function properly with Nvidia's storage controllers, but we saw it work very convincingly in our original SSD 840 EVO testing.

Click to enlarge - The new drive uses much the same hardware as the original, but on a much smaller PCB

The EVO mSATA drives again utilise Samsung's own MEX controller, a triple-core ARM-based model that operates at 400MHz, the same as before. Note that unlike the 2.5-inch drives, the mSATA ones have no casing and thus no cooling. The controller's cache is also the same, with the 1TB version offering a full 1GB of LPDDR2 for the job.

Unlike the full size models, the mSATA ones also support the DEVSLP sleep state, whereby compatible systems (e.g. Haswell based ones) can perform background tasks while operating in a very deep sleep state, much like smartphones. Samsung suggests the drive's power consumption is less than 2mW in this state, which has clear benefits for battery life in the laptop and ultra portable markets.

Finally, as well as the usual AES 256-bit encryption, the SSD 840 EVO mSATA range also comes with TCG/Opal 2.0 encryption, much like Crucial's M500, making it compatible with the eDrive protocol in Windows 8. Encrypting with your drive with BitLocker should thus have essentially zero performance impact.